1. Field of the Invention
The invention relates to alpha blending and the art of combining separate images that carry transparency or opacity information. 
2. Related Art
In some applications of computing devices, it is desirable to present a visualization of a scene to a user. Some of these applications include the following:                CAD (computer aided design);        computer aided search, such as used in the oil and gas industry;        computer simulations, such as battlefield simulations and flight simulation; and        video games, including multiplayer video games.        
A first problem in the known art is how to blend transparent (or partially transparent) components, such as for example a view of a window, a tinted window, or a translucent plastic object. This problem can occur in different computer-graphics applications. One of these applications is the blending of different computer-generated images into one image.
Known solutions include associating each pixel in the 2D (two dimensional) image with an α-value representing opacity, where “opacity” is the complement of transparency, that is, opacity+transparency=1, where opacity and transparency are each in the real-number range [0, 1]. The OpenGL standard for computing 2D/3D images has known functions for computing opacity values. Graphics hardware compatible  with the OpenGL standard implements these known functions, with the effect that a graphics programmer can take advantage of the graphics hardware's substantial additional speed with respect to a general-purpose processor.
A drawback of the known solutions is that the opacity-values of images rendered by graphics hardware do not reflect the accumulated opacity per pixel at the end of the rendering process. This accumulated opacity is necessary, if several images, independently rendered have to be correctly blended into one image. In Today's art, the opacity value at the end of the rendering process doesn't carry any usable meaning related to transparency or opacity.
A second problem in the known art is that computing an image to be presented (whether from a 2D image description, or from a 3D scene description) requires relatively large resources, including both computing power and memory.
Known solutions include breaking up computing the scene into parts, and assigning each of those parts to a separate graphics processor. These separate graphics processors each operate under control of a single controlling processor, which determines how to break up computing the scene into parts. The controlling processor sends each separate graphics processor a set of commands telling the receiver what to render. Each graphics processor generates data showing how to render its part of the scene. This data might be sent back to the controlling processor for presentation, or might be sent on to a presenting device, such as a graphics compositor, a monitor, or a set of monitors. 
The data generated by different graphic processors, sent to a controlling processor need to be blended into one correct image.
Known Methods of rendering images that generate opacity values in order to blend several pixels into one pixel generate meaningless opacity values for the final pixel. But in order to be able to blend several images into one, the conservancy of the opacity value is necessary.
One possibility might be to combine the images using software on a general-purpose processor. This possibility is subject to the drawback that a general-purpose processor would be substantially slower than graphics hardware.
Accordingly, it would be advantageous to provide methods and systems in which images might be blended and combined, which are not subject to drawbacks of the known art.
The known art includes the following documents:                R. ROST, OPENGL (ISBN 0-321-19789-5). See, e.g., page 385.        WOO, ET AL., OPENGL (3rd edition, version 1.2) (ISBN 0-201-60458-2). See, e.g., page 234.        Duff, Compositing 3D rendered images, SIGGRAPH Proceedings, 1985, pages 41-44.         Haeberli & Voorhies, 1994.        Paul Bourke, December 2002, http://astronomy.swin.edu.au/˜pbourke/colour/composite/        
No admission is made with respect to these or any other documents. 